The present invention relates to a method and apparatus for determining the validity of a data processing transaction. The invention is of particular advantage in checking the validity of a financial transaction conducted at an automatic teller machine (ATM) which has a card reader and means to enter a PIN (personal identification number).
It is conventional in an ATM to provide for an identification card to be entered and the PIN of the authorized card holder to be checked upon entry by the card holder of the PIN through a keypad of the ATM. If the PIN is entered incorrectly, the user may be allowed up to 3 attempts, and a failure to enter the correct PIN at this point may result in the capture of the card by the ATM. A PIN provides substantial security against fraudulent misuse of a card by an unauthorized user of the card, but the ATM may still not protect against misuse by an unauthorized user who may guess the PIN or who may have had access to the PIN.